Illinois Water Quality Report: 7,431 Violations Across 1,583 ZIPs
1,835 water systems · 1,583 ZIP codes · 7,431 violations · Updated 2026-05-31
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO Last verified: 2026-05-31
City Water Quality Map: Illinois
Each circle represents a city. Size indicates population, color indicates water quality grade. Tap a circle for details.
Violation Trend
EPA violations across all water systems in Illinois.
Cities with Most Violations in Illinois
| # | City | Grade | Violations | Systems | Population | |
|---|---|---|---|---|---|---|
| 1 | Chicago | C | 1,634 | 5 | 2,750,188 | Details → |
| 2 | Springfield | D | 342 | 5 | 128,012 | Details → |
| 3 | Joliet | D | 306 | 5 | 165,747 | Details → |
| 4 | Bloomington | C | 248 | 5 | 82,060 | Details → |
| 5 | Peoria | F | 232 | 3 | 143,381 | Details → |
| 6 | Rockford | F | 154 | 5 | 148,031 | Details → |
| 7 | Olney | B | 114 | 2 | 8,929 | Details → |
| 8 | Malta | D | 92 | 2 | 1,393 | Details → |
| 9 | Ottawa | C | 73 | 5 | 19,142 | Details → |
| 10 | Aurora | F | 70 | 5 | 184,170 | Details → |
Cities with Best Water Quality in Illinois
| # | City | Grade | Score | Systems | Population |
|---|---|---|---|---|---|
| 1 | Cairo | A | 85/100 | 1 | 1,821 |
Most Common Contaminants in Illinois
| Contaminant | Category | Violations | ZIPs Affected | Health Risk |
|---|---|---|---|---|
| Surface Water Treatment Rule | Treatment Technique | 1,390 | 719 | No |
| Stage 2 DBP Rule | Treatment Technique | 898 | 413 | Yes |
| Lead and Copper Rule | Treatment Technique | 825 | 397 | No |
| Stage 1 DBP Rule | Treatment Technique | 752 | 467 | Yes |
| Gross Beta | Radionuclides | 620 | 143 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 548 | 352 | Yes |
| Revised Total Coliform Rule | Microbiological | 423 | 291 | No |
| Contaminant 1006 | Other | 250 | 92 | No |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 247 | 140 | Yes |
| Fecal Coliform | Microbiological | 206 | 99 | Yes |
Water Quality Overview
Illinois has 1,835 community water systems serving approximately 14,786,766 people across 1,583 ZIP codes. These systems have accumulated 7,431 EPA violations, including 752 health-based violations.
Health-based violations account for 10% of all violations in Illinois. These violations indicate contaminant levels that may pose direct risks to human health, as opposed to monitoring or reporting failures.
Violation Breakdown
| Violation Type | Count | Percentage |
|---|---|---|
| Health-based | 752 | 10.1% |
| Monitoring/Reporting | 6,679 | 89.9% |
| Total | 7,431 | 100% |
Health-based violations indicate contaminant levels exceeding EPA Maximum Contaminant Levels (MCLs). Monitoring violations indicate failures to test or report — these do not necessarily mean unsafe water, but they mean the water was not properly verified.
Cities with Most Violations
The following cities in Illinois have the highest number of EPA violations:
| Rank | City | Grade | Violations | Water Systems | Population |
|---|---|---|---|---|---|
| 1 | Chicago | C | 1,634 | 5 | 2,750,188 |
| 2 | Springfield | D | 342 | 5 | 128,012 |
| 3 | Joliet | D | 306 | 5 | 165,747 |
| 4 | Bloomington | C | 248 | 5 | 82,060 |
| 5 | Peoria | F | 232 | 3 | 143,381 |
| 6 | Rockford | F | 154 | 5 | 148,031 |
| 7 | Olney | B | 114 | 2 | 8,929 |
| 8 | Malta | D | 92 | 2 | 1,393 |
| 9 | Ottawa | C | 73 | 5 | 19,142 |
| 10 | Aurora | F | 70 | 5 | 184,170 |
Violation counts are cumulative across all water systems serving each city. Higher counts may reflect larger systems with more monitoring requirements, not necessarily worse water quality.
Cities with Best Water Quality
These Illinois cities maintain Grade A water with zero violations:
| Rank | City | Grade | Score | Water Systems | Population |
|---|---|---|---|---|---|
| 1 | Cairo | A | 85/100 | 1 | 1,821 |
Violation Trend Over Time
Year-by-year EPA violations recorded across all water systems in Illinois:
| Year | Total Violations | Health-Based |
|---|---|---|
| 2021 | 111 | 111 |
| 2022 | 99 | 99 |
| 2023 | 130 | 130 |
| 2024 | 725 | 725 |
| 2025 | 223 | 223 |
Violations have increased from 111 in 2021 to 223 in 2025. This trend warrants monitoring and may reflect expanded testing requirements rather than worsening quality.
Most Common Contaminants
The following contaminants have caused the most violations across Illinois water systems:
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Surface Water Treatment Rule | Treatment Technique | 1,390 | 719 | No |
| Stage 2 DBP Rule | Treatment Technique | 898 | 413 | Yes |
| Lead and Copper Rule | Treatment Technique | 825 | 397 | No |
| Stage 1 DBP Rule | Treatment Technique | 752 | 467 | Yes |
| Gross Beta | Radionuclides | 620 | 143 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 548 | 352 | Yes |
| Revised Total Coliform Rule | Microbiological | 423 | 291 | No |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 247 | 140 | Yes |
| Fecal Coliform | Microbiological | 206 | 99 | Yes |
| Chlorite | Disinfection Byproducts | 159 | 117 | Yes |
How to Check Your Water in Illinois
Enter your ZIP code on ZipCheckup for detailed water system data including contaminant levels, violation history, and safety scores
Request your CCR — every water utility must provide an annual Consumer Confidence Report
Get a home test — certified kits ($20-$50) or professional lab tests ($150-$400)
Consider filtration — NSF-certified filters can address specific contaminants found in your area
EPA Enforcement
The EPA and state regulators have taken 11,842 enforcement actions against water systems in Illinois. Enforcement actions range from compliance assistance to formal orders and penalties.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Enforcement: EPA ECHO
Updated daily.
What are EPA violations?
Health-based violations mean a contaminant was detected above the EPA's Maximum Contaminant Level (MCL) — the legal limit designed to protect human health. Illinois has 752 such violations across its water systems. Not all violations cause illness, but repeated exceedances increase risk, especially for children and immunocompromised individuals.
Understanding water quality grades
ZipCheckup grades water systems from A to F based on EPA violation history, contaminant levels, and system compliance. Grade A means few or no violations; Grade F indicates persistent or serious issues. Grades are calculated per ZIP code and aggregated at the city, county, and state level.
Wondering about your tap water?
Water quality varies by ZIP code. Enter yours to see contaminant data, violations, and filtration recommendations specific to your area.
Check Your ZIP Code Water Quality →Frequently Asked Questions
Is the tap water safe to drink in Illinois?
Illinois has 1,835 community water systems with 7,431 recorded EPA violations, including 752 health-based. Water quality varies by city and ZIP code — check your specific location for detailed results.
How many water violations does Illinois have?
Illinois has 7,431 total EPA violations across 1,583 ZIP codes. 752 are health-based violations that indicate contaminant levels potentially harmful to human health. The remainder are monitoring or reporting violations.
Which city in Illinois has the worst water quality?
Chicago, IL has the most EPA violations among major cities in Illinois with 1634 recorded violations. Check individual ZIP codes for the most accurate picture of your local water quality.
Which city in Illinois has the best water quality?
Cairo, IL ranks among the best for water quality in Illinois with a grade of A. Multiple cities in Illinois maintain strong EPA compliance records.
What contaminants are found in Illinois drinking water?
Illinois water systems are monitored for over 90 EPA-regulated contaminants including lead, copper, nitrates, disinfection byproducts, and bacteria. The most common violations vary by region — check your ZIP code for contaminant-specific data.